18 



7. Monstrilla helgolandica, Glaus. 



(PI. IX) 

 Monstrilla helgolandica, Glaus. Die freilebenden Copepoden, p. 165, PI. 12, fig. 9. 



Specific Characters. Female. Body comparatively short and stout, and 

 somewhat dilated in its anterior part. Cephalic segment about occupying half 

 the length of the body and, viewed dorsally, exhibiting a somewhat fusiform 

 shape, with the greatest width a little in front of the middle and almost 

 attaining half the length. Tail of a similar shape to that in M. gracilicauda, 

 the genital segment being rather large and gradually narrowed behind; ovigerous 

 spines of moderate length. Caudal rami considerably divergent, and narrow 

 oblong in shape, each provided with 6 setae of somewhat unequal length, one 

 of them, attached somewhat dorsally, being very small, that next to it on the 

 outer side somewhat shorter than the 4 remaining ones, all the setae issuing 

 from the outermost rounded part of the ramus. Eye easily observable, and 

 having all 3 lenses distinctly developed. Antennae scarcely attaining half the 

 length of the cephalic segment, and, as in M. gracilicauda, only composed of 

 4 joints. Oral tubule well marked, and occurring about in the middle of the 

 cephalic segment. Natatory legs without any denticle inside the 2nd basal 

 segment, outer ramus less elongate than in the other species, with the terminal 

 joint of smaller size. Last pair of legs rather unlike those in the other known 

 species, each forming a narrow cylindrical stem, angularly bent in the middle 

 and tipped with 2 subequal setae. 



Body very transparent in its anterior part, but behind tinged with a dark 

 brownish pigment. 



Length, of adult female scarcely exceeding 1.40 mm. 



Male unknown. 



Remarks. This is a very small-sized species, and may moreover be 

 easily recognised by the unusual short and stout form of the body, as also 

 by the structure of the caudal rami and that of the last pair of legs. The 

 form recorded by Bourne as M. helgolandica is quite certainly not that species, 

 but more properly referable to M. longiremis Giesbrecht. 



Occurrence. Two female specimens only of this form have as yet come 

 under my notice. They were taken, many years ago, at Christiansund, west 

 coast of Norway. 



Distribution. Helgoland (Claus), Skagerak (Timm). 



